Supporting base



FIG. 1 is a perspective view of a supporting base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and

FIG. 7 is a bottom plan view thereof.

FIG. 8 is a perspective view of another embodiment of a supporting baseshowing my new design;

FIG. 9 is a front elevational view thereof;

FIG. 10 is a rear elevational view thereof;

FIG. 11 is a left side elevational view thereof;

FIG. 12 is a right side elevational view thereof;

FIG. 13 is a top plan view thereof; and,

FIG. 14 is a bottom plan view thereof.

Portions in broken lines are for illustrative purposes only and form nopart of claimed design.

The ornamental design for a supporting base, as shown and described.